I have never understood the research and permutations gardeners go through to determine how and when to fertilize things like tomatoes. Or roses. Gardeners have been growing them successfully for decades before all that technical nonsense was available online. There is no need to reinvent the wheel :-))

If growing in containers in a soil-less mix, use a waters soluble fert with all necessary macro and micro nutrients like Dyna Gro's Foliage Pro or GROW. You have the option of fertilizing with every watering or weekly and the dosage is clearly spelled out.

For plants growing in the ground, a dedicated tomato fertilizer, like Espoma's Tomato Tone or Dr. Earth's Tomato and Vegetable fertilizer, applied according to label directions, will supply all the necessary nutrients for healthy and productive growth.

I use Tomato Tone every 2 weeks. It's all they need.

I use horse manure or mushroom compost and no other fertilizer. I judge how much I need by the looks of the soil. If I see too much clay I add more. If I have a clump of clay in the center of the plot I'm working I throw in a shovel more in that spot. I don't get soil tests. I do add some lime or wood ashes and whatever weeds are in the ground I'm digging up.